Control valves are commonly employed in fluid or gas distribution systems to control the pressure in the system downstream of the control valve. The pressure at which a gas distribution system supplies gas may vary according to the demands placed on the system, the climate, the source of the supply, and/or other factors. However, most end-user facilities equipped with, for example, gas appliances such as furnaces, ovens, etc., require the gas to be delivered in accordance with predetermined pressure parameters. Therefore, such distribution systems use control valves to ensure that the delivered gas meets the requirements of the end-user facilities.
In fluid or gas control valves (collectively “fluid control valves”), a number of design and performance considerations may be important. For example, designers of fluid control valves may strive to design control valves that have greater pressure stability and reduced sensitivity to inlet pressure variations. Further, designers may strive to construct more compact designs, and designs which might favor easy assembly and service.
Several types of fluid control valves are known, for example, sliding stem control valves, rotary control valves, etc. In some control valves fluid flow through the valve is turned by 90 degrees or more as the fluid passes through a valve seat. The 90 degree turn is necessary because an actuator for the valve is oriented generally perpendicular to the fluid flow direction and a valve plug is oriented parallel to actuator movement (i.e., perpendicular to the fluid flow direction) to simplify the actuator-valve plug interface. However, in some applications some control valves may suffer from vibration and loss of valve efficiency due to the turning fluid flow path through the regulator.
Axial or in-line flow control valves are an alternative to control valves having a 90 degree turn. Axial flow valves have a flow path or passageway through the valve that is substantially straight or parallel to the fluid flow direction to minimize turbulent flow through the valve body. While the flow path or passageway may not be exactly straight or parallel, the flow path or passageway may include a turn that is significantly less than 90 degrees, which can reduce vibrations and losses of efficiency.
Axial flow control valves typically include an actuator mounted to an exterior surface of a valve body. The actuator is operatively coupled to a flow control member of the valve and moves the flow control member between an open position and a closed position to allow or prevent the flow of fluid through the valve. Some known axial flow control valves actuate a flow control member within the valve body relative to a seat ring to control fluid flow through the valve body.
However, axial flow control valves suffer from the need for precise internal machining and long assembly times.